25.4.3.2 Planning the Options You Want

Keep in mind that you must set several limits, more than one of which
might cause the rotation or deletion of a log file. Whichever limit is reached
first is the controlling one. For example, if your maximum log-file size is
3.5 MB, and you specify that a new log be created every day, you may actually
get log files created faster than one per day if log data builds up faster
than 3.5 MB every 24 hours. Then, if your maximum number of log files is 10
and your maximum age is 8 days, you may never reach the age limit on log files
because the faster log rotation may mean that 10 files will have been created
in less than 8 days.

The following default values, provided for Messaging Server administration
logs, may be a reasonable starting point for planning:

Maximum number of log files in a directory: 10

Maximum log-file size: 2 MB

Total maximum size permitted for all log files: 20 MB

Minimum free disk space permitted: 5 MB

Log rollover time: 1 day

Maximum age before expiration: 7 days

Level of logging: Notice

You can see that this configuration assumes that server-administration
log data is predicted to accumulate at about 2 MB per day, backups are weekly,
and the total space allotted for storage of admin logs is at least 25 MB.
(These settings may be insufficient if the logging level is more verbose.)

For POP, IMAP or HTTP logs, the same values might be a reasonable start.
If all services have approximately the same log-storage requirements as the
defaults shown here, you might expect to initially plan for about 150 MB of
total log-storage capacity. (Note that this is meant only as a general indication
of storage requirements; your actual requirements may be significantly different.)